The present disclosure generally relates to the manufacture of semiconductor devices, and more particularly, to an ultraviolet assisted pore sealing process for porous low k dielectric materials employed in semiconductor devices.
As semiconductor and other microelectronic devices progressively decrease in size, the demands placed on device components continue to increase. For example, the prevention of capacitive crosstalk between interconnect lines becomes significantly more important with smaller devices. Capacitive crosstalk is generally a function of both the distance between conductors and the dielectric constant (k) of the material placed in between the conductors. Considerable attention has been focused on electrically isolating the conductors from each other using new insulators having low dielectric constants because although silica (SiO2), which has traditionally been used in such devices because of its relatively good electrical and mechanical properties, however as devices scale to smaller dimensions dielectric constants below SiO2's value of about 4 are required. These new low k (i.e., a dielectric constant less than 4) materials are desirable for use, for example, as inter-layer dielectrics (ILD).
To achieve low dielectric constants, one can either use a material that possesses a low dielectric constant, and/or introduces porosity into the material, which effectively lowers the dielectric constant because the dielectric constant of air is nominally 1. Porosity has been introduced in low k materials through a variety of means. In the case of spin-on low k dielectrics, a lowering of the k value can be achieved by using high boiling point solvents, by using templates or by porogen based methods. However, the integration of porous low-k materials in the manufacture of the semiconductor device, in general, has proven difficult.
For example, because of the open nature of the porous low k dielectric materials, process gases and chemistries employed in subsequent processing (i.e., after formation of the porous low k dielectric material)) may diffuse into the porous network where they become trapped where they can cause damage as well as alter the dielectric constant. Moreover, pores in direct communication with the surface can cause pinholes to form in subsequent layers deposited and/or formed thereon, e.g., barrier layers.
Accordingly, there is a need in the art to provide improved methods towards porous low k dielectric materials for integration into semiconductor devices. Because of at least the problems noted with the prior art, it would be desirable to seal the porous low k dielectric prior to depositing additional layers and/or prior to further processing. Sealing the surface of the porous low k dielectric will advantageously prevent penetration (and trapping) of process gases and chemistries. Moreover, sealing will provide a continuous surface layer for coating/depositing additional layers thereon. Consequently, pinhole formation in subsequent layers can be substantially prevented.